Loudspeaker

ABSTRACT

A loudspeaker including a diaphragm, means for driving said diaphragm, an annular suspension member of rubberlike elastic material attached to the marginal edge of said diaphragm and a supporting frame to which said suspension member is fixed, characterized in that said suspension member has a relatively large radial width and a tapered thickness which gradually decreases from the outer peripheral portion to the inner peripheral portion, and said member is fixedly connected at said outer peripheral portion to the supporting frame and at said inner peripheral portion to said marginal edge of the diaphragm.

United States Patent Feb. 29, 1972 Sotome [54] LOUDSPEAKER [72]Inventor: Hiromi Sotorne, Hamamatsu, Japan [73] Assignee: Nippon GakkiSeizo Kabushiki Kaisha,

l-lamamatsu-shi, Japan [22] Filed: Dec. 23, 1970 [21] App]. No.: 100,959

[30] Foreign Application Priority Date Dec. 26, 1969 Japan ..44/104291[52] US. Cl. ..181/32 R [51] Int. Cl. ...Gl0lt 13/00, H04r 7/00 [58]FieldoiSearch ..181/32 R,31 R, 24

[56] Reierenees Cited UNlTED STATES PATENTS 1,832,832 11/1931 Nagelvoort..181/32 R 2,863,520 12/1958 Manley et a] ..181/32 R FOREIGN PATENTS ORAPPLICATIONS 369,992 3/1932 Great Britain ..l8l/32 R PrimaryExaminer-Stephen J. Tomsky Attorney-Henry T. Burke, Robert Scobey,Robert S. Dunham, P. E. Henninger, Lester W. Clark, Gerald W. Griffin,Thomas F. Moran, R. Bradlee Boal, Christopher C. Dunham and John F.Scully [57] ABSTRACT 1 Claim, 5 Drawing Figures PATENTEDFEB29 I9723,645,356

I NVENTOR. f/mo/wl Sara/14.5

BY /WM ATM/FIVE? BACKGROUND OF THE INVENTION The present inventionrelates to a loudspeaker. More particularly, it relates to a suspensionfor supporting a marginal edge of a diaphragm of a loudspeaker onto asupporting frame.

l-Ieretofore, various forms of suspension have been used to support anedge of a diaphragm of a loudspeaker. Typical forms are shown in FIGS.1, 2 and 3.

FIG. I shows a suspension in which a diaphragm l is formed at its edgeportion with a corrugation 2, whose outer periphery in turn is fixed atits periphery on a supporting frame 3. In such a suspension, theavailable amplitude of the diaphragm can be increased by increasing thenumber of waves of the corrugation 2 or increasing the radial width ofthe suspension portion, but the suspension portion having a large radialwidth and being macroscopically of flat shape, tends to produce freevibration, which will cause deep dips in the frequency characteristic ofthe loudspeaker.

FIG. 2 shows a suspension in which a diaphragm 11 has, adhered to themarginal portion thereof, a roll-shape suspension 12 whose outerperiphery in turn is fixed to a supporting frame 13. This suspension hasan advantage over the one shown in FIG. I, in that relatively largeavailable amplitude can be obtained with relatively narrow radial widthof the suspension, which is of unflat shape. The larger availableamplitude, however, cannot be obtained without the increase of theradial width and the corresponding increase of radius of curvature ofthe roll-shape suspension. The increase of the radius of curvaturecauses extreme decrease of the strength of the suspension itself so thatthe suspension may produce resonance in opposite phase relative to thatof the diaphragm or it may be adversely affected by the vibrating air onthe front and rear sides of the diaphragm.

FIG. 3 shows a suspension in which a diaphragm 21 is attached at itsperiphery to a suspension sheet member 22 made of foamed urethane or thelike material, whose outer periphery in turn is fixed on a supportingframe 23. The suspension of FIG. 3 produces good results in the smallamplitude range, but it has the same defects as explained with referenceto FIG. 1 in the large amplitude range.

SUMMARY OF THE INVENTION It is a general object of the present inventionto provide a loudspeaker which eliminates the disadvantages of the priorart as noted above.

It is a particular object to provide a loudspeaker in which a radialwidth of an edge portion is increased so that a large availableamplitude can be obtained with small deformation of the suspension bodyitself.

It is another object of the present invention to provide a loudspeakerhaving a suspension which provides lesser free vibration and greaterdamping action than those of the prior art, and which has sufl'rcientstrength to resist the vibrating air on the front and rear sides of thediaphragm, so that few and little peaks and dips appear in the frequencycharacteristic throughout the whole sound range from low to highfrequency sound.

It is a further object of the present invention to provide a loudspeakerin which lowest resonance frequency can be easily lowered so thatsatisfactorily low-frequency sound can be reproduced even when mountedin a small cabinet.

In accordance with the present invention there is provided a loudspeakerwhich comprises a diaphragm, means for driving said diaphragm, anannular suspension member of elastic material, such as rubber, attachedto the marginal edge of said diaphragm, said annular suspension memberhaving a relatively large radial width and a tapered thickness whichgradually decreases from its outer peripheral portion to its innerperipheral portion, and a supporting frame to which said annularsuspension member is fixed at the outer peripheral portion thereof.

DESCRIPTION OF DRAWINGS FIGS. 1, 2 and 3 are sectional views, showingdiaphragm suspension portions of three conventional types ofloudspeaker, respectively; and

FIGS. 4 and 5 are sectional views, showing diaphragm suspension portionsof two forms of loudspeaker according to the present invention,respectively.

DETAILED DESCRIPTION Referring the the drawings, FIG. 4 shows a fomi ofa loudspeaker according to the present invention, which includes adiaphragm 31 driven by any conventional driving means (not shown), anannular suspension member 32 made of rubberlike elastic materialattached to the marginal edge of said diaphragm and a supporting frame33 to which said annular suspension member is fixed, said annularsuspension member 32 having a relatively large radial width. Saidsuspension member 32 has an increased thickness at its outer peripheralportion 34, which is fixed on the supporting frame 33. The thicknessgradually decreases from the outer peripheral portion 34 toward itsinner peripheral portion 35 to which the marginal edge of the diaphragmis adhered.

FIG. 5 shows another form of a loudspeaker according to the presentinvention, which includes a diaphragm 41, a suspension member 42 and asupporting frame 43. The construction of these elements is substantiallysame as that shown in FIG. 4, except that the marginal edge of thediaphragm 41 is not adhered to the inner peripheral surface of thesuspension member, as shown in FIG. 4, but inserted into and fixedlyheld by a groove formed in the inside peripheral surface of the annularsuspension member 42.

In practice, the radial width of the annular suspension member as shownin FIGS. 4 and 5 for supporting the diaphragm having the diameter of30-40 cm. or more may be about 3-l0 cm., depending on the size of thediaphragm or the setting of the lowest resonance frequency, and thethickness of said member at the outer peripheral portion fixed on thesupporting frame may be about 5-20 mm.

Although two forms of the connection between the diaphragm and thesuspension member are illustrated in FIGS. 4 and 5, such connection maybe constructed in other forms. For example, the diaphragm and thesuspension member may be overlapped together over the larger width ofconnection, in order to avoid the occurrence of abrupt boundarycondition change which would produce reflection of vibration.

It will be understood that the present invention provides a loudspeakerin which a large available amplitude can be obtained since the diaphragmis supported at its marginal edge on the supporting frame through therelatively wide annular suspension member made of rubberlike elasticmaterial, and a flat frequency characteristic is obtained because thetapered form of said suspension member serves to reduce the resonance ofthe suspension portion and smoothly absorb the vibration. The suspensionmember, which is made of nIbberlike elastic material, has good dampingand vibration-absorbing property. Because the suspension member hasgradually reduced thickness toward its inside periphery, it producesunder any vibrating frequency the vibration of only minimum mass portionof said member required to obtain the amplitude corresponding to saidvibrating frequency, and consequently good radiation efficiency and goodtransient property can be obtained. The suspension member, which isthick and durable, serves to improve the durability andweather-resistant property of a loudspeaker. The loudspeaker canreproduce lowfrequency sound even when mounted in a small cabinet inview of the fact that the lowest resonance frequency can be easilylowered.

I claim:

1. A loudspeaker comprising a diaphragm, means for driving saiddiaphragm, an annular suspension member of elastic material, and asupporting frame, said annular suspension member having a relativelylarge radial width and a tapered thickness which gradually reduces fromits outer peripheral portion to its inner peripheral portion and saidmember being fixedly connected at said inner peripheral portion to themarginal edge of said diaphragm and at said outer peripheral portion tosaid supporting frame.

* a a: a e 5

1. A loudspeaker comprising a diaphragm, means for driving saiddiaphragm, an annular suspension member of elastic material, and asupporting frame, said annular suspension member having a relativelylarge radial width and a tapered thickness which gradually reduces fromits outer peripheral portion to its inner peripheral portion and saidmember being fixedly connected at said inner peripheral portion to themarginal edge of said diaphragm and at said outer peripheral portion tosaid supporting frame.